docs: def _fetchBlock(self):
          """ internal use only.
  	 get a block of rows from the server and put in standby block.
           future enhancements:
           (1) locks for multithreaded access (protect from multiple calls)
           (2) allow for prefetch by use of separate thread
          """
          # make sure that another block request is not standing
          if self._blockRequestInProgress :
             # need to wait here before returning... (TODO)
             return
  
          # make sure another block request has not completed meanwhile
          if self._standbyBlock is not None: 
             return
  
          self._blockRequestInProgress = True
          fetchReq = TFetchResultsReq(operationHandle=self.operationHandle,
                                      orientation=TFetchOrientation.FETCH_NEXT,
                                      maxRows=self.arraysize)
          self._standbyBlock = self._fetch([],fetchReq)
          self._blockRequestInProgress = False
          return